Electric motor heating/cooling system

ABSTRACT

An electric motor includes a case, a stator that includes a stator laminaiton and end-windings, a rotor coupled to the case via at least one rotor bearing. The rotor includes a hollow cylindrical body, a first shaft portion, and a second shaft portion. The hollow cylindrical body includes an inner wall, an outer wall, a first distal end, and a second distal end. The first shaft portions couples to the first distal end and the second shaft portion couples to the second distal end. The second shaft portion includes a fluid feed tube formed therewith having a fluid receive end and a fluid feed end, the fluid feed end extending to a central inner portion of the hollow cylindrical body. A plurality of fluid exit ports adjacent the first distal end and the second distal end of the hollow cylindrical body spray fluid onto components of the stator.

CROSS-REFERENCE TO RELATED APPLICATION

The present application claims priority claims priority pursuant to 35U.S.C. § 120 and U.S.C. § 365(c) as a continuation of InternationalApplication Ser. No. PCT/US2017/036285, entitled “ELECTRIC MOTOR COOLINGSYSTEM’, filed 7 Jun. 2017, which claims priority pursuant to 35 U.S.C.§ 119(e) to U.S. Provisional Patent Application No. 62/346,741, entitled“ELECTRIC MOTOR COOLING SYSTEM AND ROTOR DISCHARGE PROTECTION’, filed 7Jun. 2016, both of which are incorporated herein by reference in theirentirety and made part of the present application for all purposes.

BACKGROUND Technical Field

The present invention relates to electric motors; and more particularlyto the management of the temperature of an electric motor.

Description of Related Art

Electric motors can generate considerable heat, especially by thetraction motor of a vehicle where size and weight constraints arecoupled with the need for high power output. Electric motor overheatingcauses the motor winding insulation to deteriorate quickly. For every10-degree Celsius rise in electric motor temperature, insulation life iscut in half. Another issue caused by overheating is that permanentmagnets in the rotor lose their magnetic properties as they overheat,resulting in a loss of efficiency. For induction motors, an increase intemperature of their copper windings reduces efficiency of the inductionmotor—copper electrical resistivity increases 4% for every 10-degreeCelsius temperature increase. Thus, it is important to cool the internalmotor components (e.g., rotor) as well as the outer motor components(e.g., case, stator). The electric motor cooling system must operateefficiently over large variations in ambient operating environment asthe electric motor may be subjected to a wide range of ambienttemperatures, humidity levels, and/or dust/dirt levels.

A number of different approaches have been taken to meeting the coolingdemands placed on a vehicle's electric motor. For example, U.S. Pat. No.6,191,511 discloses using a closed loop, liquid cooling circuit in anattempt to achieve a temperature balance within the motor, the coolingcircuit passing the coolant (typically a fluid such as oil, e.g.,automatic transmission oil or similar type oil) through both the statorand a hollow rotor shaft. Within the hollow rotor shaft is a stationaryinjection tube, the injection tube fixed to a stator flange. The fluidis pumped through the injection tube to the end of the rotor shaft whereit is passed between the cavity of injection tube and the hollow rotorshaft. The fluid then passes through a cylindrical cooling chamberextending over the length and periphery of the stator before cooling thestator structure and being returned to the injection tube.

U.S. Pat. No. 6,329,731 discloses a liquid cooled electric motor inwhich one of the main elements of the planetary gear drives thedisplacement pump of a cooling circuit. Fluid is pumped through astationary tube about which the hollow rotor shaft rotates. The fluidthen passes between the stationary tube and the hollow rotor shaftbefore passing through a radiator incorporated into the motor andplanetary gear casing.

U.S. Pat. No. 7,156,195 discloses an electric motor in which fluid iscollected within the reduction gear case, not the motor case, thusavoiding deterioration and alteration of the motor magnets. The fluidfrom the reservoir is pumped through the end of a passage in the driveshaft where it flows toward the motor. Some of the fluid is sprayed ontothe reduction gears while the rest of the fluid is pumped between thedrive shaft and the reduction gear shaft and the motor output shaft.

These prior solutions had a number of shortcomings. They failed toaddress the differing heat production locations along the length of therotor. More heat tends to be generated in the central portion of therotor, as compared the end or distal portions of the rotor. The priorart solutions tended to cool using a fluid that flowed from one distalportion of the rotor to another distal portion of the rotor, causing aheat gradient from end to end and end to rotor center. Further, theprior art solutions included a number of relatively complex parts,resulting in relatively high production costs and a relatively highfailure rate.

Another problem with the operation of battery powered electric vehiclesis that the powering batteries do not operate efficiently at lowtemperatures. As the deployment of electric vehicles proliferates, manyare used in environments having cold winters and/or in locations thatare cold at all times. In order to keep the electric vehicles operatingat a reasonable efficiency level, the electric vehicles must be storedinside or use externally powered battery heaters to keep the batteriesat an acceptable operating temperature. This solution, of course, doesnot work when a heated storage location is unavailable or when externalpower is not available.

SUMMARY

According to a first embodiment of the present disclosure, an electricmotor includes a case, a stator having a stator lamination andend-windings, and a rotor coupled to the case via at least one rotorbearing. The rotor includes a hollow cylindrical body, a first shaftportion, a second shaft portion and a plurality of fluid exit ports. Thehollow cylindrical body includes an inner wall, an outer wall, a firstdistal end, and a second distal end. The first shaft portion couples tothe first distal end of the hollow cylindrical body. In alternateembodiments, the electric motor is an induction motor. The second shaftportion couples to the second distal end of the hollow cylindrical bodyand includes a fluid feed tube formed therewith having a fluid receiveend and a fluid feed end, the fluid feed end extending to a centralinner portion of the hollow cylindrical body. The plurality of fluidexit ports resides adjacent the first distal end and the second distalend of the hollow cylindrical body and are configured to spray fluidonto at least the end-windings of the stator.

With the rotor structure of the electric motor, a fluid, e.g., oil,serves to heat or cool the rotor during operation. Further, with therotor structure of the electric motor, the cooling fluid also serves toheat or cool the end-windings of the stator and/or the statorlamination. With the fluid flow caused by the structure of the rotor ofthe present disclosure, a single mechanism supports both rotor coolingand stator end-winding cooling.

The electric motor may include a number of additional features andstructures. These features and structures may be included in variouscombinations that include some of these features and structures, all ofthese features and structures, or one of these features and structures.The electric motor may include a drive motor fluid pump configured topump the fluid into the fluid receive end of the fluid feed tube.

The fluid feed end of the fluid feed tube may include a plurality offluid spray ports formed in the second shaft portion and configured tospray fluid onto the inner wall of the hollow cylindrical body. With theelectric motor, a distance from the central inner portion of the hollowcylindrical body to the plurality of fluid exit ports may be based upona specified fluid film thickness to support rotor cooling.

The electric motor may include a cylindrical laminated stack thatincludes a plurality of permanent magnets coupled to the outer wall ofthe hollow cylindrical body. The electric motor may include a drivemotor fluid pump having a drive motor fluid pump outlet and a drivemotor fluid pump inlet. The electric motor may further include fluidcirculation piping having an output portion coupled between the drivemotor fluid pump outlet and the fluid receive end of the second shaftportion, an input portion coupled between a fluid collection point onthe case and the drive motor fluid pump inlet and drive motor fluid pumpelectronics. The electric motor may further include a radiatorconfigured to cool the fluid. The electric motor may further include aheat exchanger coupled between the drive motor fluid pump and theradiator.

According to a second embodiment of the present disclosure, a method foroperating an electric motor includes pumping fluid into a hollowcylindrical body of a rotor via a fluid feed tube that is oriented alongan axis of rotation of the rotor. The method further includes sprayingthe fluid from a plurality of fluid exit ports of the fluid feed tubeonto an inner wall of the hollow cylindrical body of the rotor, thefluid further flowing along an inner wall of the hollow cylindrical bodyfrom a central portion towards fluid exit ports located adjacent distalends of the hollow cylindrical body. The method then includes sprayingthe fluid from the fluid exit ports onto at least end-windings of astator of the electric motor.

The method serves to heat or cool the rotor, the stator laminate and/orthe end-windings of the stator. With the fluid flow of this method, asingle operation supports both rotor heating/cooling, stator laminateheating/cooling, and stator end-winding heating/cooling.

The method of operating the electric motor may include a number ofadditional operations and/or features. These operations and/or featuresmay be included in various combinations that include some of theseoperations and/or features, all of these operations and/or features, orone of these operations and/or features. The method may include sprayingthe fluid from the plurality of fluid exits ports onto the inner wall ofthe hollow cylindrical body by spraying the fluid onto a central portionof the inner wall of the hollow cylindrical body. The fluid flows alongthe inner wall of the hollow cylindrical body to the plurality of fluidexit ports. With the method, a distance from the central inner portionof the hollow cylindrical body to the plurality of fluid exit ports maybe based upon a specified fluid film thickness to support rotorheating/cooling.

The method may further include circulating the fluid from the electricmotor to a heat exchanger, cooling the fluid by the heat exchanger, andcirculating the fluid from the heat exchanger to the electric motor. Themethod may further include circulating coolant between a radiator andthe heat exchanger. The method may additionally include circulating thecoolant between the heat exchanger and a battery. Further, the methodmay include adjusting flow of the fluid based upon a temperature of therotor, coolant temperature, coolant flow, rotor speed, and electricmotor torque, among other parameters.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 illustrates the basic components of a battery powered electricvehicle.

FIG. 2 illustrates components of a drive motor and battery thermalmanagement system, both constructed and operating according to adisclosed embodiment.

FIG. 3 illustrates components of a drive motor and a portion of thecomponents of a drive motor thermal management system according to adisclosed embodiment.

FIG. 4 illustrates components of a drive motor and a portion of thecomponents of a drive motor thermal management system according to adisclosed embodiment, particularly showing the manner in which fluid andheat flow.

FIGS. 5A and 5B illustrate a rotor according to a representativeembodiment, detailing the construct of fluid exit ports within a hollowcentral portion of the rotor.

FIGS. 6A, 6B, 6C, and 6D illustrate operation of a drive motor accordingto one or more embodiments of the present disclosure.

FIG. 7 is a flow diagram illustrating electric motor and battery thermalmanagement operations according to a disclosed embodiment.

DETAILED DESCRIPTION OF THE DISCLOSURE

FIG. 1 illustrates the basic components of a battery powered electricvehicle (electric vehicle) 100. The electric vehicle 100 includes atleast one drive motor (traction motor) 102A and/or 102B, at least onegear box 104A and/or 104B coupled to a corresponding drive motor 102Aand/or 102B, a battery 106 and electronics 108 (including drive motorelectronics). Generally, the battery 106 provides electricity to theelectronics 108 of the electric vehicle 100 and to propel the electricvehicle 100 using the drive motor 102A and/or 102B. The electric vehicle100 includes a large number of other components that are not describedherein but known to one or ordinary skill. While the construct of theelectric vehicle 100 of FIG. 1 is shown to have four wheels, differingelectric vehicles may have fewer or more than four wheels. Further,differing types of electric vehicles 100 may incorporate the inventiveconcepts described herein, including motor cycles, aircraft, trucks,boats, train engines, among other types of vehicles.

Various operational issues with the electric vehicle 100 are describedherein in conjunction with various embodiments. One of these operationalissues relates to the cooling of the drive motor 102A or 102B. Anotherof these operational issues relates to control of operating temperatureof the battery 106. Subsequent description herein may relate back to thecomponents of this FIG. 1. Common numbering may be used to refer tocomponents identified in further FIGs. described herein.

FIG. 2 illustrates components of a drive motor and battery thermalmanagement system 200, both constructed and operating according to adisclosed embodiment. The drive motor and battery thermal managementsystem 200 includes a drive motor thermal management system 202 havingone or more drive motor fluid pumps 204, a fluid reservoir 206 andelectronics 208. In the illustrated embodiment, the fluid is oil, e.g.,automatic transmission oil, lubricating oil, or similar oil. In otherembodiments, other types of fluid may be used. The drive motor fluidpump 204 pumps fluid between the drive motor 102A and/or 102B, the fluidreservoir 206, and a heat exchanger 210. In one embodiment, the heatexchanger 210 exchanges heat from or to the fluid with water or glycolbased coolant and routes the water or glycol based coolant to a radiator212 for cooling. The heat exchanger 210 may include another pump tocirculate the water or glycol based coolant to battery 106 via coolanttubes 214. In other embodiments, the drive motor fluid pump 204 maycouple directly to the coolant tubes 214 of the battery 106 and/or tothe radiator 212 when a common fluid is used. The drive motor fluid pump204 is controlled by electronics 208, which may include a digitalcomputer, memory, and/or data processing and controlling components. Thedrive motor fluid pump 204 may include control valves to control flow offluid between the drive motor 102A and/or 102B, the reservoir 206, andthe heat exchanger 210 (and battery 106 coolant tubes 214 in otherembodiments). The heat exchanger 210 may also include valves to directthe flow of coolant to the battery 106 coolant tubes 214 and to theradiator 212, under control of electronics 208 in some embodiments.

Further illustrated in FIG. 2 are drive motor electronics 216 thatreceive electrical power from the battery 106 and power the drive motor102A and/or 102B. The drive motor electronics 216 include powerelectronics and control electronics. The power electronics may includean inverter to drive a stator of the drive motor 102A and/or 102B. Thecontrol electronics may include processing circuitry and memory. Theprocessing circuitry may be a central processing unit, customizedcontrol circuitry, or other circuitry that is configured to executesoftware instructions and process data. The memory may include RAM, ROM,DRAM, static RAM, flash RAM, flash ROM, or another type of memorycapable of storing software instructions and/or data.

FIG. 3 illustrates components of a drive motor 102A (or 102B) and aportion of the components of a drive motor thermal management system 200according to a disclosed embodiment. The drive motor 102A includes acase 302, a stator 331 coupled to the case 302 that includes a statorlamination 304 and end-windings 305, stator drive electronics (notshown), at least one rotor bearing coupled to the case (not shown inFIG. 3), and a rotor 303 coupled to the case 302 via at least one rotorbearing. The rotor 303 includes a hollow cylindrical body 308 having aninner wall 310, an outer wall 312, a first distal end, and a seconddistal end. The rotor 303 also includes a first shaft portion 314coupled to a first distal end of the hollow cylindrical body 308 and asecond shaft portion 316 coupled to a second distal end of the hollowcylindrical body 308. The second shaft portion 316 includes a fluid feedtube 318 formed therewith having a fluid receive end 320 and a fluidfeed end 322. The fluid feed end 322 extends to a central inner portionof the hollow cylindrical body 308. The fluid feed end 322 of the secondshaft portion 316 includes a plurality of fluid spray ports 324configured to spray fluid onto the inner wall 310 of the hollowcylindrical body 308. The rotor 303 also includes a plurality of fluidexit ports 326 formed adjacent the first distal end and second distalend of the hollow cylindrical body 308.

A distance from the inner wall 310 of the hollow cylindrical body 308 tothe plurality of fluid exit ports 326 is based upon a specified fluidthickness to support rotor cooling while the rotor 303 rotates, e.g.,when the motor 102A is causing movement of a serviced vehicle 100 orwhile the rotor is stationary. Such specified fluid thickness is basedupon viscosity of the fluid, rotational velocity of the rotor 303, andtemperature of the fluid. The relationship between the inner wall 310,the plurality of fluid exit ports 326, and the specified fluid thicknesswill be described further with reference to FIGS. 4 and 5.

The rotor 303 also includes a cylindrical laminated stack 306 coupled tothe outer wall 312 of the hollow cylindrical body 308. The cylindricallaminated stack 306 includes a plurality of permanent magnets andinsulating material. The stator 331 includes a plurality of statorwindings (not shown) that are intercoupled by the stator end-windings305. In alternate embodiments, the electric motor is an induction motor.

The drive motor fluid pump 204 (each drive motor fluid pump when thereare multiple drive motor fluid pumps) has a drive motor fluid pumpoutput 307 and a drive motor fluid pump input 309. The drive motorcooling system 200 includes fluid circulation piping having an outputportion coupled between the drive motor fluid pump output 307 and thefluid receive end 320 of the rotor second shaft portion 316. Further,the fluid circulation piping includes an input portion coupled between afluid collection opening 311 in the case 302 and the drive motor fluidpump input 309. The drive motor fluid pump electronics 208 direct thedrive motor fluid pump 204 (and associated valves) to pump fluid fromthe reservoir 206 into the fluid receive end 320 of the fluid feed tube318. The fluid is recirculated to the drive motor fluid pump 204 via thefluid collection opening 311 in the case 302. The stator driveelectronics and the drive motor fluid pump electronics are designed tooperate in an inactive mode, a waste heat mode, and a rotor/statorcooling mode, and a rotor/stator heating mode.

In the waste heat mode, the stator drive electronics provide electricalpower to the stator 331 with or without causing rotation of the rotor303. Further, in the waste heat mode, the drive motor fluid pump 204 mayat least substantially fill the hollow cylindrical body 308 with fluid.This waste heat mode operation causes the drive motor fluid pump 204 tocirculate fluid on end-windings 305 of the stator 331 to heat the fluid.As will be shown further with reference to FIGS. 6A, 6B, 6C, and 6D,fluid diversion structure(s) may be included to direct the fluid uponthe end-windings 305. The fluid may further be directed to the a of thestator to heat the stator lamination 304 for more efficient operation.The waste heat generated from the end-windings 305 of the stator 331 andfrom the stator lamination 304 is collected by the fluid and circulatedto the heat exchanger 210. The heated fluid may then be routed to thecoolant tubes 214 of the battery to heat the battery 106. Theseoperations are described further herein with reference to FIG. 7.

In the rotor/stator thermal management mode, the stator driveelectronics provide electrical power to the stator 331 to cause rotationof the rotor 303 based upon the power requirements of the drivingsituation of the electric vehicle 100. Further, the drive motor fluidpump 204 circulates fluid to manage the operating temperature of therotor 303 and the stator 331 of the electric motor. The drive motorfluid pump 204 circulates the fluid to the heat exchanger 210. The heatexchanger 210 may heat or cool the fluid or use heat from the fluid forbattery 106 warming. In another operation, heat from the battery 106 isused to warm the rotor 303 and/or the stator 331.

FIG. 4 illustrates components of a drive motor 102A and a portion of thecomponents of a drive motor thermal management system according to adisclosed embodiment, particularly showing the manner in which fluidflows. Numbering between FIGS. 3 and 4 is consistent with arrowsincluded in FIG. 4 to illustrate fluid flow and heat flow. Solid arrowedlines in FIG. 4 indicate fluid flow. Dashed arrowed lines indicate heatflow. Note that there is shown to be a gap between the stator lamination304 and the outer portion of the rotor 303. This gap is exaggerated toillustrate that fluid may flow between the rotor 303 and the stator 331.

Fluid (oil in the embodiment of FIG. 4) enters the fluid feed tube 318at the fluid receive end 320. The fluid feed tube 318, which may be aforged internal extension of the second shaft portion 316, transportsthe fluid towards the fluid feed end 322 of the second shaft portion316. fluid exits the fluid feed tube 318 via fluid spray ports 324 atthe fluid feed end 322. The pressure of pumping of the fluid at thefluid feed end 322 and centrifugal force when the rotor 303 is spinningcauses the fluid to be received upon the inner wall 310 of the hollowcylindrical body 308. When the rotor 303 is spinning, as indicated atbox reference number 3 of FIG. 4, the oil builds up a layer on a centralportion of the inner wall 310 and runs along the inner wall 310 towardsthe fluid exit ports 326. As indicated at box reference number 4 of FIG.4, the fluid exits the rotor 303 via the fluid exit ports 326 providingconstant flow and heat transport.

Note that in FIGS. 3 and 4, the one or more drive motor fluid pumps 204are not a regular coolant pump. The fluid that the drive motor fluidpump 204 pumps through the rotor 303 cannot be water/glycol fluid, whichis not dielectric liquid, but is oil and, thus, the drive motor fluidpump 204 is an oil pump in embodiments described herein. Further, therotor heating/cooling structure and method described herein may be usedwith any other stator heating/cooling method. The rotor heating/coolingdescribed herein may be in series or in parallel with one or more statorcooling branches.

FIGS. 5A and 5B illustrate a rotor 303 according to a representativeembodiment, detailing the construct of fluid exit ports within a hollowcentral portion of the rotor 303. As shown, fluid exits the fluid exitports 326 from the interior of the rotor 303. In the waste heat mode,the drive motor drive motor fluid pump fills the hollow cylindrical body308 with fluid and the fluid is forced out of the fluid exit ports 326by the pressure of the pumped fluid when inside the hollow cylindricalbody 308.

Referring to all of FIGS. 4, 5A and 5B, during the rotor/statorheating/cooling mode, the centrifugal force caused by the rotor's 303rotation causes the fluid to form a film on the inner wall 310 of thehollow cylindrical body 308. Thickness of the film as it moves along theinner wall is based upon a distance from the outermost portion of thefluid exit ports 326 and the inner wall 310 as well as fluid propertiessuch as viscosity and temperature, angular velocity of the rotor 303,and other factors. The fluid flows from a central portion of the innerwall 310 to distal portions of the hollow cylindrical body 308 in whichthe plurality of fluid exit ports 326 are formed. The fluid is at afirst temperature when it exits the fluid spray ports 324 and iscollected on the inner wall 310 at the central portion. As the fluidflows along the inner wall 310 towards the distal ends of the hollowcylindrical body 308 it collects heat from the rotor 303 and the fluidis at a second temperature, which is higher than the first temperature.Thus, with the structure of the rotor cooling system, more cooling isprovided to a central portion of the rotor 303, at which more heat isgenerated. This benefit results in more uniform temperature control ofthe rotor 303.

FIGS. 6A, 6B, 6C, and 6D illustrate operation of a drive motor accordingto one or more embodiments of the present disclosure. The rotor 303includes at least one oil distribution ring 602 fixed to the rotor 303.The oil distribution ring 602 deflects fluid (oil) exiting the hollowcylindrical body 308 via the fluid exit ports 326 towards the statorend-windings 305. Deflection of the fluid is performed both during thewaste heat mode and the rotor/stator cooling mode. FIG. 6A details theoil distribution ring 602 located on a proximal end of the rotor 303.FIG. 6B shows fluid flow (direction of arrow) from the inside of thehollow cylindrical body 308, out of fluid exit port 326, against the oildistribution ring 602, and towards the stator end-windings 305. FIG. 6Cillustrates fluid flow from the oil distribution ring 602 towards thestator end-windings 305. FIG. 6D illustrates fluid flow from fluid exitport 326 past the laminated stack 306 towards the stator end-windings305. With the embodiment of FIG. 6D, fluid is directed from the rotordirectly to the end windings 305 without entering the air gap betweenthe rotor and the stator, which would increase drag and reduceefficiency of the electric motor.

FIG. 7 is a flow diagram illustrating electric motor cooling and batteryheating operations 700 according to a disclosed embodiment. As shown,the electric motor cooling and battery heating operations include aninactive mode (step 702), a waste heat mode (step 704) and arotor/stator cooling mode (step 718). The inactive mode (step 702) isused when the electric car is not being used, when the battery 106 is inan acceptable operating temperature range, and/or when the rotor/statordo not require cooling. The waste heat mode (step 704) is enacted whenthe thermal management of the battery 106 (or another component of theelectric vehicle 100) requires warming of the battery 106. In coldlocations, the temperature of the battery 106 may be as low as −30degrees Fahrenheit due to ambient temperature. In order for the battery106 to be sufficiently functional to drive the electrical vehicle 100,the temperature of the battery 106 must be raised to at least −10degrees Fahrenheit. The waste heat mode (step 704) serves this purpose.

In waste heat mode, the stator of the electric motor is powered to heatend-windings of the stator (and other portions of the stator 331 as wellas the rotor 303) with or without causing the rotor 303 of the electricmotor to rotate (step 706). Stator 331 powering without rotor 303rotation may be accomplished by applying DC voltage/current to thestator windings by the stator drive electronics. Alternately, stator 331powering without rotor 303 rotation may be accomplished by applying thesame AC drive signal to each of the phases of the stator windings. Notethat limited rotor 303 rotation may be accomplished by the stator 331operating inefficiently to cause the rotor 303 to generate heat whilerotating. The drive motor fluid pump 204 is then operated to pump fluidinto the hollow cylindrical body 308 of the rotor 303 (step 708). Suchpumping continues until the hollow cylindrical body 308 is at leastsubstantially filled. By continuing pumping until the hollow cylindricalbody 308 is filled, fluid exits the hollow cylindrical body 308 via thefluid exit ports 326 and flows onto the stator end-windings 305, thestator lamination 304, and in the air gap between the rotor 303 andstator 331 where the fluid gathers heat from the contacted components(step 710). The oil distribution ring 602 may assist in directing thefluid onto the stator end-windings 305 and the stator lamination 304.The operation of step 710 may result in the case 302 of the electricmotor being at least substantially filled with fluid. The heated fluidis then pumped to heat exchanger 210 to heat coolant circulatingtherethrough (step 712). The heated coolant is then circulated via thecoolant tubes 214 to heat the battery 106 (step 714). The fluid heatingand circulation operations are continued until the battery is heated toan acceptable operating temperature (as determined at step 716). Oncethe battery is heated to the acceptable operating temperature, operationreturns to the inactive mode (step 702).

The waste heat mode may commence with first warming the drive motorfluid pump 204 and fluid to an acceptable operating temperature. In oneembodiment, the drive motor fluid pump 204 is submerged in the fluidreservoir 206 and acts as a small heater for the fluid. In such case,the drive motor fluid pump 204 is operated very inefficiently to produceonly heat and to produce enough torque to move locally the fluid throughthe system. A goal in this operation is to transfer heat from the drivemotor fluid pump 204 to the fluid as quickly as possible. Once the drivemotor fluid pump 204 and fluid are warmed, the waste heat mode maycontinue to warm the battery 106. Local hot spots allow to drive motorfluid pump 204 to suck in fluid and around the drive motor fluid pump204 into the downstream cooling and lubrication system by sucking coldoil in at the same time. This cold oil will be heated up subsequently,which will raise the fluid temperature even faster to continue with thewaste heat mode.

The waste heat mode operations 704 of FIG. 7 may be performed usingdiffering rotor and stator structures than those described previouslyherein. For example, a differing fluid feed tube structure may be usedto feed the fluid into the hollow cylindrical body 308 of the rotor. Insuch example, the fluid feed tube may be separate from the shaft of therotor. Further, differing structure may be employed for the fluid toexit the hollow cylindrical body 308 of the rotor and/or to be directedonto the end-windings 305 of the stator and the stator lamination 304.

In the rotor/stator cooling mode (step 718), the stator is at leastpartially enabled to rotate the rotor as required to propel the electricvehicle 100 (step 720). Fluid is pumped into the hollow cylindrical body308 by the drive motor fluid pump 204 at a selected flow rate (step722). The fluid flows along the inner wall 310 of the hollow cylindricalbody 308 towards the distal ends of the hollow cylindrical body 308,collecting heat from the rotor 303 along the way, and then exits thehollow cylindrical body 308 via the fluid exit ports 326 towards theend-windings 305 of the stator, the stator lamination 304, and the airgap between the rotor 303 and the stator 331 (step 724). The fluid isthen optionally routed to the heat exchanger 210 for heating/cooling ofthe fluid (step 726). If a flow rate adjustment is necessary to alterthe cooling rate (as determined at step 728), the fluid flow rate ismodified (step 730). If not, operation returns to step 722. Therotor/stator heating/cooling mode is ceased when the car ceasesoperations or if the rotor/stator no longer needs heating/cooling.

In the foregoing specification, the disclosure has been described withreference to specific embodiments. However, as one skilled in the artwill appreciate, various embodiments disclosed herein can be modified orotherwise implemented in various other ways without departing from thespirit and scope of the disclosure. Accordingly, this description is tobe considered as illustrative and is for the purpose of teaching thoseskilled in the art the manner of making and using various embodiments ofthe disclosed system, method, and computer program product. It is to beunderstood that the forms of disclosure herein shown and described areto be taken as representative embodiments. Equivalent elements,materials, processes or steps may be substituted for thoserepresentatively illustrated and described herein. Moreover, certainfeatures of the disclosure may be utilized independently of the use ofother features, all as would be apparent to one skilled in the art afterhaving the benefit of this description of the disclosure.

Routines, methods, steps, operations, or portions thereof describedherein may be implemented through electronics, e.g., one or moreprocessors, using software and firmware instructions. A “processor”includes any hardware system, hardware mechanism or hardware componentthat processes data, signals or other information. A processor caninclude a system with a central processing unit, multiple processingunits, dedicated circuitry for achieving functionality, or othersystems. Some embodiments may be implemented by using softwareprogramming or code in one or more digital computers or processors, byusing application specific integrated circuits (ASICs), programmablelogic devices, field programmable gate arrays (FPGAs), optical,chemical, biological, quantum or nano-engineered systems, components andmechanisms. Based on the disclosure and teachings representativelyprovided herein, a person skilled in the art will appreciate other waysor methods to implement the invention.

As used herein, the terms “comprises,” “comprising,” “includes,”“including,” “has,” “having” or any contextual variants thereof, areintended to cover a non-exclusive inclusion. For example, a process,product, article, or apparatus that comprises a list of elements is notnecessarily limited to only those elements, but may include otherelements not expressly listed or inherent to such process, product,article, or apparatus. Further, unless expressly stated to the contrary,“or” refers to an inclusive or and not to an exclusive or. For example,a condition “A or B” is satisfied by any one of the following: A is true(or present) and B is false (or not present), A is false (or notpresent) and B is true (or present), and both A and B is true (orpresent).

Although the steps, operations, or computations may be presented in aspecific order, this order may be changed in different embodiments. Insome embodiments, to the extent multiple steps are shown as sequentialin this specification, some combination of such steps in alternativeembodiments may be performed at the same time. The sequence ofoperations described herein can be interrupted, suspended, reversed, orotherwise controlled by another process.

It will also be appreciated that one or more of the elements depicted inthe drawings/figures can also be implemented in a more separated orintegrated manner, or even removed or rendered as inoperable in certaincases, as is useful in accordance with a particular application.

1. An electric motor comprising: a case; a stator that includes a statorlamination and end-windings; and a rotor coupled to the case via atleast one rotor bearing, the rotor comprising: a hollow cylindrical bodyhaving an inner wall, an outer wall, a first distal end, and a seconddistal end; a first shaft portion coupled to the first distal end of thehollow cylindrical body; a second shaft portion coupled to the seconddistal end of the hollow cylindrical body, the second shaft portionincluding a fluid feed tube formed therewith having a fluid receive endand a fluid feed end, the fluid feed end extending to a central innerportion of the hollow cylindrical body; and a plurality of fluid exitports adjacent the first distal end and the second distal end of thehollow cylindrical body configured to spray fluid onto at least theend-windings of the stator.
 2. The electric motor of claim 1, furthercomprising: at least one drive motor fluid pump configured to pump thefluid into the fluid receive end of the fluid feed tube; and a fluidreservoir.
 3. The electric motor of claim 1, wherein the fluid feed endof the fluid feed tube comprises a plurality of fluid spray ports formedin the second shaft portion and configured to spray fluid onto the innerwall of the hollow cylindrical body.
 4. The electric motor of claim 1,further comprising a cylindrical laminated stack coupled to the outerwall of the hollow cylindrical body and including a plurality ofpermanent magnets.
 5. The electric motor of claim 1, wherein a distancefrom the central inner portion of the hollow cylindrical body to theplurality of fluid exit ports is based upon a specified fluid filmthickness to support rotor cooling.
 6. The electric motor of claim 1,further comprising: a drive motor fluid pump having a drive motor fluidpump outlet and a drive motor fluid pump inlet; fluid circulation pipinghaving: an output portion coupled between the drive motor fluid pumpoutlet and the fluid receive end of the second shaft portion; an inputportion coupled between a fluid collection point on the case and thedrive motor fluid pump inlet; and drive motor fluid pump electronics. 7.The electric motor of claim 6, further comprising a radiator configuredto cool the fluid.
 8. The electric motor of claim 7, further comprisinga heat exchanger coupled between the drive motor fluid pump and theradiator.
 9. A rotor for use with a stator having a stator laminationand end-windings, the rotor comprising: a hollow cylindrical body havingan inner wall, an outer wall, a first distal end, and a second distalend; a first shaft portion coupled to the first distal end of the hollowcylindrical body; a second shaft portion coupled to the second distalend of the hollow cylindrical body, the second shaft portion including afluid feed tube formed therewith having a fluid receive end and a fluidfeed end, the fluid feed end extending to a central inner portion of thehollow cylindrical body; and a plurality of fluid exit ports adjacentthe first distal end and the second distal end of the hollow cylindricalbody configured to spray fluid onto at least the end-windings of thestator.
 10. The rotor of claim 9, further comprising at least one rotorbearing that rotatingly couple the rotor to the stator.
 11. The rotor ofclaim 9, wherein the fluid feed end of the fluid feed tube comprises aplurality of fluid spray ports formed in the second shaft portion andconfigured to spray fluid onto the inner wall.
 12. The rotor of claim 9,further comprising a cylindrical laminated stack coupled to the outerwall of the hollow cylindrical body and including a plurality ofpermanent magnets.
 13. The rotor of claim 9, wherein a distance from thecentral inner portion of the hollow cylindrical body to the plurality offluid exit ports is based upon a specified fluid film thickness tosupport rotor cooling.
 14. A method for operating an electric motorcomprising: pumping fluid into a hollow cylindrical body of a rotor viaa fluid feed tube that is oriented along an axis of rotation of therotor; spraying the fluid from a plurality of fluid exit ports of thefluid feed tube onto an inner wall of the hollow cylindrical body of therotor, the fluid further flowing along the inner wall of the hollowcylindrical body from a central portion towards fluid exit ports locatedadjacent distal ends of the hollow cylindrical body while the rotor isrotating; and spraying the fluid from the fluid exit ports onto at leastend-windings of a stator of the electric motor.
 15. The method of claim14, wherein spraying the fluid from the plurality of fluid exits portsonto the inner wall of the hollow cylindrical body comprises sprayingthe fluid onto a central portion of the inner wall of the hollowcylindrical body.
 16. The method of claim 15, wherein a distance fromthe central inner portion of the hollow cylindrical body to theplurality of fluid exit ports is based upon a specified fluid filmthickness to support rotor cooling.
 17. The method of claim 14, furthercomprising: circulating the fluid from the electric motor to a heatexchanger; exchanging heat between the fluid and the heat exchanger; andcirculating the fluid from the heat exchanger to the electric motor. 18.The method of claim 17, further comprising circulating coolant between aradiator and the heat exchanger.
 19. The method of claim 18, furthercomprising circulating the coolant between the heat exchanger and abattery.
 20. The method of claim 14, further comprising adjusting flowof the fluid based upon at least a temperature of the rotor.